What forces the high voltage to jump the gap at the spark plug?

The correct answer focuses on the collapse of the primary magnetic field, which plays a crucial role in the ignition system of an engine. When the ignition coil is energized, it creates a magnetic field. As the coil is quickly de-energized, this magnetic field collapses rapidly. This collapsing magnetic field induces a high voltage in the secondary winding of the ignition coil.

When this high voltage reaches the spark plug, it provides enough electrical energy to overcome the resistance of the air gap between the electrodes of the spark plug, allowing the electric current to jump across the gap and create a spark. This spark ignites the air-fuel mixture in the engine cylinder, facilitating combustion.

Other factors, although relevant in various contexts of engine performance, do not directly create the necessary voltage to jump the gap at the spark plug. For example, the size of the spark plug gap and the resistance of the ignition coil influence spark characteristics, but they are not the mechanisms that generate the high voltage itself. Meanwhile, the temperature of the engine affects engine performance and the combustion process, but it does not play a direct role in the voltage generation process at the spark plug during ignition.